1. Field of the Invention
The present invention relates to a microwave oven, and more particularly to a microwave oven for automatically grounding a printed circuit board to a body of a microwave oven when the printed circuit board is fastened to a control panel.
2. Description of the Prior Art
Generally, a microwave oven is designed to generate microwaves to heat and cook the food, where the microwave oven is disposed at a body thereof with a control panel equipped with a manipulating key.
The printed circuit board (hereinafter referred to as PCB) for electrically controlling the microwave oven according to a signal input through the manipulating key is fastened and fixed to an inner side of the control panel.
In the conventional microwave oven thus constructed and illustrated in FIG. 1, the PCB 1 is secured to a plastic control panel 3 by way of a plurality of screws (2-1, 2-2, 2-3 and 2-4).
At this location, a ground pattern formed at the PCB 1 and a body 4 of the microwave oven made of steel are connected by a ground wire 5 to thereby ground the PCB 1 to the body 4 of the microwave oven.
However, there is a problem in a ground structure of a PCB according to the prior art thus constructed, in that a separate ground wire 5 must be pulled out of the PCB 1 to be connected to the body 4, which leads to inconveniences in assembly of the microwave oven.
Furthermore, there is another problem in that an operator often forgets to connect the ground wire 5 to the body 4 of the microwave oven to thereby cause a safety problem because the PCB 1 is not grounded to the body 4.
Meanwhile, an example of a microwave oven disclosed in Japanese Patent Application Laid-Open Publication No. Hei-8-233286 has a construction where a PCB is screwed to an inner side of a panel disposed with a manipulating key, so that a screw fastening member cannot be forgotten in fastening.
In the microwave oven thus constructed as illustrated in FIG. 2, the PCB is formed with a screw hole through which the PCB is fastened via a fastening screw to an inner side of the panel disposed with a manipulating key.
At this time, the PCB is formed with a screw hole which in turn renders same unconductive, but the PCB is rendered conductive by way of the screw being plugged into the screw hole.
Accordingly, a microcomputer 10 connected to the PCB can discriminate whether or not a screw is inserted thereinto according to a potential of the PCB.
The conventional microwave oven thus constructed can only discriminate whether or not a screw for fixing the PCB to a control panel is accurately fastened.